Generally, semiconductor devices contain multiple levels of conductor wiring. As lithographic dimensions have reduced, and the degree of device integration has increased, these structures have become increasingly planar. This trend is projected to continue into the sub 0.25 micron regime by most major semiconductor fabricators.
One disadvantage of this industry trend is that the relatively thick dielectric layers necessary to reduce parasitic wiring capacitance make the incorporation of intentional conductor to conductor capacitors very area intensive. This is compounded by relatively poor capacitance tracking due to thickness variation in the planarized dielectrics. Capacitive elements are critical to many circuit applications. High capacitance per unit area is essential for cost effective design.
Previous versions of thin film capacitor devices were found unsatisfactory because of capacitor dielectric defects due to irregularities in an etched metal capacitor plate, dielectric defects at the edge of the capacitor plate, and leakage around the capacitor plate because of conductive residues.